Power supply circuits are utilized in electronic devices to provide continuous operation. For example, a television set utilizes a power supply circuit to provide electrical power for reception and transmission of broadcast, cable or satellite signals to a user. Many electronic devices include a standby mode which provides electrical power to an electronic device for activating such devices for normal operation. Again for example, a present-day television set is equipped with a low power stand-by power supply circuit, to activate the television set and operate at times when the television set is in a power-off mode.
The stand-by power supply circuit provides electrical power to a micro-controller and infra-red receiver such that the power-on may be accomplished by a remote control at any time. Contrary to what the term “stand-by power supply” implies, the stand-by power supply circuit does not stop working when the television set is in power-on mode, the circuit also remains fully operational in power-on mode to keep delivering electrical power to the micro-controller and other digital circuits. In essence, stand-by power supply circuits provide continuous electrical power to electronic devices both in power-on and power-off modes.
Growing awareness to environmental pollution in the United States of America (U.S.) and abroad has resulted in the Energy Star program developed by the U.S. Department of Energy and introduced in the U.S. in 1997 by the U.S. Environmental Protection Agency. The Energy Star regulations enacted in the U.S. are expected to cut environmental waste and decrease power consumption. However, a drastic reduction in power consumption leads to a decreased operational efficiency for electronic devices due to a necessarily over-rated specification and operation of the stand-by power supply circuit. For example, reduction in power consumption of the stand-by power supply circuit does not obliterate the increase power needed for operation of an AC relay. As the need for reduced power consumption grows it would be desirable to provide electronic devices that reduce power consumption without producing resulting operational inefficiencies.